New irrigation effects study counter to what Christy discovered

This press release below from Columbia University shown below suggests that irrigation cools the region undergoing irrigation. However, a study published three years ago of California’s central valley by Dr. John Christy suggests exactly the opposite. See this WUWT post from 2007, then read the Columbia story and decide for yourself.

A two-year study of San Joaquin Valley nights found that summer nighttime low temperatures in six counties of California’s Central Valley climbed about 5.5 degrees Fahrenheit (approximately 3.0 C) between 1910 and 2003. The study’s results will be published in the “Journal of Climate.”

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Irrigation can have a major cooling effect in some regions. Credit: U.S. Department of Agriculture.

Expanded irrigation has made it possible to feed the world’s growing billions—and it may also temporarily be counteracting the effects of climate change in some regions, say scientists in a new study. But some major groundwater aquifers, a source of irrigation water, are projected to dry up in coming decades from continuing overuse, and when they do, people may face the double whammy of food shortages and higher temperatures. A new study in the Journal of Geophysical Research pinpoints where the trouble spots may be.

“Irrigation can have a significant cooling effect on regional temperatures, where people live,” said the study’s lead author, Michael Puma, a hydrologist who works jointly with Columbia University’s Earth Institute and its affiliated NASA Goddard Institute for Space Studies. “An important question for the future is what happens to the climate if the water goes dry and the cooling disappears? How much warming is being hidden by irrigation?”

Scientists generally agree that in the last century, humans have warmed the planet about .7 degrees C (about 1.3 degrees F) by pumping vast amounts of carbon dioxide into the air. How much warmer earth will get depends not only on future carbon emissions but an array of other variables. For instance, earth’s oceans and vegetation have been absorbing a growing share of emissions, but recent studies suggest this uptake may be slowing. This could lead to more carbon dioxide in the air, and accelerated warming. On the other hand, humans are also cooling the planet to some degree, by releasing air-polluting particles that lower temperatures by reflecting the sun’s energy back into space. Pumping of vast amounts of heat-absorbing water onto crops is lowering temperatures in some regions as well, say the authors.

Scientists are just beginning to get a handle on irrigation’s impact. In a hundred years, the amount of irrigated farmland has grown four-fold, now covering an area four times the size of Texas. Puma and his coauthor, Benjamin Cook, a climatologist at Goddard and Columbia’s Lamont-Doherty Earth Observatory, are the first to look at the historic effects of mass watering on climate globally by analyzing temperature, precipitation and irrigation trends in a series of model simulations for the last century. They found that irrigation-linked cooling grew noticeably in the 1950s as irrigation rates exploded, and that more rain is now falling downstream of these heavily watered regions.

In warm, dry regions, irrigation increases the amount of water available for plants to release into the air through a process called evapotranspiration. When the soil is wet, part of the sun’s energy is diverted from warming the soil to vaporizing its moisture, creating a cooling effect. The same process explains why drying off in the sun after a swim at the beach can be so refreshing.

Globally, irrigation’s effect on climate is small—one-tenth of one degree C (about 0.2 degree F). But regionally, the cooling can match or exceed the impacts of greenhouse gases, say the scientists. For example, the study found some of the largest effects in India’s arid Indus River Basin, where irrigation may be cooling the climate up to 3 degrees C, (5.4 degrees F) and up to 1-2 degrees C in other heavily irrigated regions such as California’s Central Valley and parts of China. The study also found as much as .5 degree C cooling in heavily watered regions of Europe, Asia and North America during the summer.

The study suggests also that irrigation may be shaping the climate in other ways, by adding up to a millimeter per day of extra rain downwind of irrigated areas in Europe and parts of Asia. It also suggests that irrigation may be altering the pattern of the Asian monsoon, the rains that feed nearly half of the world’s population. These findings are more uncertain, the authors caution, and will require further research.

“Most previous modeling studies were idealized experiments used to explore potential impacts, but this is a much more realistic simulation of the actual impacts,” said David Lobell, a Stanford University scientist who studies climate impacts on agriculture and was not involved in the study. “Their results show some interesting differences by time period and region that will lead to more research and contribute to more accurate simulations of future climate, particularly in agricultural areas.”

Irrigation has increased because it boosts crop yields, supporting many millions of small farmers, said Upmanu Lall, head of the Columbia Water Center at the Earth Institute. But concern is growing that groundwater supplies in India and China may not keep up. “Near term and future climate predictions are essential for anticipating climate shocks and improving food security,” he said. “The study points to the importance of including irrigation in regional and global climate models so that we can anticipate precipitation and temperature impacts, and better manage our land, water and food in stressed environments.”

“These findings are more uncertain”- ” This is a more realistic simulation” they say.
I say BS. They just want more money to carry on more simulations. The people in the U.S. , I hope are sick of this crap and will hopefully wake up soon.

GHG’s, according to all I am aware of, holds heat.
that is supposedly why night time temps are up.
I wonder if people in the Sahara or Gobi would be interested in knowing that at night the water vapor would make things cooler.
Here in the Gulf Coast, I think people will be surprised to find that humid air is cooler than dry air.

Christy’s said that nightime temps were increasing, but he didn’t say that total average temps were increasing. His study simply said that with substantial water available during the day, the water absorbed heat, and then released it at night, raising nighttime temps.

Is this necessarily different from the conclusions of the new study?

The new study says that water absorbs heat during the day, and then that some of the water (the part that doesn’t remain on the ground to release heat at night) evaporates, so that that part of heat created by the sun doesn’t remain on the ground but instead is transferred to water which leaves the area to perhaps rain downwind. Hence cooling during the day and likely daily average cooling.

If you follow the link above back to the 2007 post on Christy’s study, you will see that Anthony did some analysis on Chico’s daily temps, and found — consistent with Christy — that nighttime temps were increasing for the last century. He also found — consistent with the new study — that daytime and daily average temps were decreasing with time, presumably as increased acreage became irrigated between 1900 and 2000.

Please correct me if I’m wrong, but where is the contradiction between these two studies?

It is soooo typical for warmists to take the simplistic approach which assumes, more or less, that global warming is happening and that any instance of it not being apparent must be a short-term masking of global warming. After all they KNOW it is happening, duh, so any time it is not, must be a temporary setback.

Irrigation also has an effect on the weather.
A friend of mine grew up in Montana in an area of dry land farming.
As she grew older, more and more land was irrigated, and summertime afternoon thunderstorms began to be commonplace.
As more land was irrigated, those thunderstorms became a daily occurrence.
Certainly, somebody has done a study about this effect, which should be an expected resullt of the introduction of more water vapor into a previously-arid hot climate.

Once again, the authors have no idea what valleys were like prior to controlled river levels and irrigation. Wallowa valley was considered too wet for crops when first settled by whites. The Nez Pierce Indians knew this too. Once river flooding was controlled and irrigation ditches built, LESS water was spread throughout the valley than before. MORE water stayed in the rivers. The soil dried enough on the valley floor to grow grass and alfalfa with a wheat field here and there (most of the dry crops were raised on hillsides and on top of the surrounding higher plains).

Before the dams were built along the Snake and Columbia, the same thing occurred. The land was SWAMPY! Once river levels were controlled, more water stayed in the river with some of it pumped out when the farmers needed it as opposed to washing over the land during floods, whether you needed it or not.

Would irrigation act similiar (but not the same) to the ocean?. Cooling effect in summer, warming effect in winter – in other words a moderating influence. I understand the ocean is a body of water as compared to a spray/thin layer of water. It would also depend on the temperature of the ground water and the comparable air temperature.

1950 and beyond does NOT support any of their assessments or conclusions. Measurement, as typical, is the only issue. I might be convinced of a “land use issue” for the southern San Joaquin Valley (No good GHCN stations), but not irrigation. Sacramento seems to have more “adjustments” in the “non-adjustment” data (Running cooler than the Davis Farm in the past 20 years).

As a glider pilot we always avoided irrigation areas because there were less thermals there in the daytime becuase of the cooling effect. But I would expect temperatures to be higher than surrounding areas during the night due to the extra humidity.

Overall there would be cooling due to the evaporation but also heating due the albedo change of the land.

It´s vegetation, it´s plant life. Plants and trees have a real interchange between ground and the atmosphere, much more than computer models and modellers in air-conditioned rooms with artificial light could ever imagine.
To understand this just think in post normal science and “modern” specialization: How in the world a “climate scientist” or an “ecologist”watching 8 hours a day at a computer screen can know about nature. It´s impossible.
Where there have been built or made irrigations of many types, the most inmediate consequence it has been an increase in humidity and even in deserts it has began raining.
These phenomena have been known by millenia until “illustration”tag it as “ignorance”, “superstition”, etc.
We, “modern and presumptuosly evolved men”, have trashed real science to replace it by child games and wishes, we have trashed, also, sanity, health from our lives.
Back in the “underdeveloped” neolithic times, cromlechs, trilithons, had a precise purpose on managing the “field” that, unless we trash our self indulgement and consideration about what the other people may think or say about “us”; we, the nice and intelligent guys who know everything, as mommy and daddy taught us to believe.
As Herman Hesse´s character Magister Ludi in “The Glass bed game” called this era: “The pamphlet Era”.

Pamela Gray- exactly, well put. Grande Ronde Valley has a similar history. My family did dry land wheat and cattle in both Washington and NE Oregon, and the benefits of irrigation and power are tremendous. Now we have “Hay Duke” Kitzhaber D-Retread
runnning for Oregon Governor, who wants to kill that flood control on the Snake, by blowing up the Snake River Dams.
The Grande Ronde and Wallowa Valleys will be covered with wind machines,
no people, or animals, imho, but that is what the appear to want…

Central California has had a huge increase in smog in the last 40 years. I mean huge. Bakersfield used to be visible 40 miles away. Now you can’t make detail but a couple miles away. The smog is mostly is and around the fields. And it is due to the inversion and a perverse mix of vapors I have been told by residents of Central California. Manure, nitrous oxide, a bit of water vapor, ammonia, diesel fumes,etc. If someone said that it was a localized heat sump, i would not be surprised.
I suspect that in areas where industrial and transport exhaust is less, where ranches were rarer, and the agriculture was mere vegetation irrigation might have a cooling effect.

This study confirms the findings of previous research on the cooling effect of irrigation on daytime temps. Over large areas the addition of so much water vapor does have regional effects on temp, convection and precip. Christy’s study seemed to focus more on nighttime temps.

This is a good example of a mesoscale anthropogenic impact which has little or no direct connection to CO2. Global average temperature is a hollow metric. People live in regional climates where variations are much larger than the global average.

intrepid_wanders-Christy et al did not use GHCN for the SJV, in point of fact Christy painstakingly gathered data from the area that wasn’t available from GHCN or USHCN. The number of stations used is vastly more. So before you criticize, you ought to know exactly what was done. Please see for yourself:

John-The contradiction is that what Christy generally found was that where there was warming in the minimum, the maximum temperatures did NOT cancel the warming, as they remained fairly steady. They found that both maximum and minimum temps were pretty stable in the mountains, but the valley saw net warming. This study says that the cooling of maximum temps would be greater than the minimum temps, I think. Precisely the opposite seems to happen. Now WHY is that? The reason is because climate models do not handle the boundary layer dynamics behind this discrepancy very well. There are a number of things that I could say about this, but I just recommend this:

Bernie says:
September 8, 2010 at 6:03 pm
As a glider pilot we always avoided irrigation areas because there were less thermals there in the daytime becuase of the cooling effect. But I would expect temperatures to be higher than surrounding areas during the night due to the extra humidity.

And darker plowed fields generate more heat than do fileds covered with stalks.

There is a simple way to test their “simulations.” Study areas that were traditionally arid and that are now becoming wetter due to land use changes (new irrigation projects). Southeastern New Mexico, with lots of huge pecan orchards in middle of the desert, would be a good starting point, assuming that there is any decent long-term historical data on humidity and air temp.

Bernie @ 6:03 PM
Welcome. Excellent observation. When your life is on the line, you do tend to notice things like updrafts and downdrafts.
I am not sure of the protocol but I have been commenting since the start of this site. Can we come to some arrangement?

“But some major groundwater aquifers, a source of irrigation water, are projected to dry up in coming decades from continuing overuse, and when they do, people may face the double whammy of food shortages and higher temperatures.”

“Irrigation can have a significant cooling effect on regional temperatures, where people live,” said the study’s lead author, Michael Puma, a hydrologist who works jointly with Columbia University’s Earth Institute and its affiliated NASA Goddard Institute for Space Studies. “An important question for the future is what happens to the climate if the water goes dry and the cooling disappears? How much warming is being hidden by irrigation?”

So… a tiny percentage of the global land mass is irrigated and they are suggesting that this negates 15% of the effects of GHG’s planet wide, all sources, and including any warming that was built up over the decades before irrigation became prevalent? While I doubt the numbers, I find the assumption that human activity will potentially result in some catastrophic change in the environment that will spell disaster that we cannot survive the more interesting topic.

This assumption that we humans are destined to be the victims of mother nature’s whims are simply not borne out by the evidence. The fact is that humans dominate this planet precisely because we are capable of exterting a measure of control over our environment, and a greater level of control than the alarmists want to admit. Consider the case above. The fear expressed is that the acquifers supplying the irrigation systems may dry up, exposing us to both a sudden jump in global temperatures and a sudden drop in food supply. Scary, scary, scary.

The fact is that even if the acquifer does dry up, it is highly unlikely to do so instantly. It would happen over a period of years at a minimum, but more likely decades. Consider the options we as humans have. Yes, desalinating sea water and pumping it overland to replace the water from the acquifers would be energy intensive and expensive, but the point is we could do it, and the cooling effect of irrigation claimed in the study above would far more than off set the emissions from fossil fuel used to accomplish the task. Nuclear would be even better. Alternatively, Canada is home to 10% of the world’s fresh water while occupying a fraction of the global land area. While diverting rivers in Canada to supply fresh water for irrigation in the US would galvanize protests from the environmentalists, the point is that while it is not currently politicaly correct, accomplishing this feat is well within our technological capabilities and when the choice becomes divert or starve, the environmental objections tend to get drowned out. Either solution is fine with me, as a red neck Canuck I am happy to sell the US the oil or uranium to power desalination, or the fresh water instead.

This notion that mankind is destined to be the helpless victim of his own effects on the environment is true only if one assumes that environmental change by default causes our collective IQ to drop to the level of an ape. Hooo hooo hah hoo, not gonna happen.

Christy actually says that the daytime temps cooled, even as the nighttime temps warmed:

“While nighttime temperatures have risen, there has been no change in summer nighttime temperatures in the adjacent Sierra Nevada mountains. Summer daytime temperatures in the six county area have actually cooled slightly since 1910. Those discrepancies, says Christy, might best be explained by looking at the effects of widespread irrigation.”

That is from the 2007 presser you can access from the link above. So both studies agree on more daytime cooling the last century. No disagreement.

Wonderfully articulated! I can’t even add to your statement other than to reiterate man’s ability to move water. Many may find this inconceivable, but I’m pretty sure it can still happen.

I knew they’d make a play for water, in fact, if one looks back, I’m sure I stated as much here. But it still amazes me how people believe we can’t, couldn’t, or wouldn’t be able to handle some H2O displacement. Heat = more evaporation, which = more rain, which would, or should allay the fears of the alarmists, yet, inexplicably, they are still afraid of water going away. Ladies!!! Water doesn’t go anywhere!!! It’s ok, take your panties out of the wad and relax. We can move it from A to B and even create electricity while we do it!! It’s ok. Just calm down.

The phenomenon is, in my opinion, more important than some seem to think. It goes right to the heart of the entire GHG theories, and I am a bit surprised that more work hasn’t been done on testing the models on the Regional scale that is way easier to study and get good data from than the globe is.

The phenomenon is, in my opinion, more important than some seem to think. It goes right to the heart of the entire GHG theories, and I am a bit surprised that more work hasn’t been done on testing the models on the Regional scale that is way easier to study and get good data from than the globe is.
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That’s because it blows their world up. More heat = more evaporation, which = more rain. If it gets colder, then less H2O is available for the cycle. They can’t really discuss it beyond the sophistry demonstrated in the story above, else, too many thoughts would be expounded upon it. Water isn’t a problem.

This is quite interesting from several points of view. One is more back up to the contention that local climate can be effected by human activities, all be it in this case quite small. I think Roy Spencer has written about this as has Roger Pielke Sr. Another is the point that some aquifers are being over drawn and this is not a good long term idea. Without the full study to read all we really know is what the press release gives and my experience has been press releases are almost always misleading. My experience in Alberta suggests the general conclusions given at least make sense. Another issue not mentioned is the rather wasteful methods of delivering water to many crops in many areas. I have noticed some improvements by some farmers here in Alberta over the last 5 or 6 years, however.

Fascinating discussion. I am wondering, just how far from home does that solar energy go? I am thinking the solar energy invested in evaporation (in this case, of irrigation water) is matched by the energy released during condensation; energy released to the atmosphere, raising the temperature of the air. Cooling here, warming there.

Lots of glider pilots on this forum, I have noticed. Any glider pilot anticipates “overdevelopment” (convective cloud generating rain showers) first and worst (because it puts us on the ground tout suite) over areas that experienced showers last night, or in this case and as was mentioned in a previous post areas that experienced irrigation recently. The point is, in a glider pilot’s world, the evaporation frequently leads to condensation within a few miles laterally and within a mile or even less vertically. So has there been any change in energy within the volume encompassed by a typical convective cell?

Irrigation has increased because it boosts crop yields, supporting many millions of small farmers, said Upmanu Lall, head of the Columbia Water Center at the Earth Institute. But concern is growing that groundwater supplies in India and China may not keep up.

Oh yes, and there it is, doom and gloom awaits us all, save the Earth, stop irrigation. Think of the poor small farmers in India and China, Donate generously and quickly.

“Alternatively, Canada is home to 10% of the world’s fresh water while occupying a fraction of the global land area. While diverting rivers in Canada to supply fresh water for irrigation in the US . . .”

The humidity is raised due to irrigating. This increases the heat capacity of the atmosphere. This means more heat energy is required to raise the atmosphere’s temperature and more heat energy needs to be lost to lower the atmosphere’s temperature. This makes the high temperatures lower and the low temperatures higher, as was shown by the first study.

The rest is BS.

The highest temperatures are recorded where there is the least amount of green house gases (where the humidity is the lowest).

Here are some side affects of diverting flood waters into river channels.

Ground water is found further below the surface than it used to be. Those massive floods kept land in a perpetual swamp. That also meant that shallow hand-dug wells had swampy flavored water in them. When the flood waters were prevented, ground water levels sunk and so did the wells, resulting in better tasting water (and quite a few dry wells that had to be deepened or drilled).

After irrigation ditches and gates replaced untimely flooding (same amount of water overall being spread out, but diverted to where it was needed and controlled better), the folks that get their knickers in a twist over fish getting caught in irrigation ditches decided to fish screen them. Suddenly, much of the spawning ground was cut off and restricted to the fast moving rivers. No flooded valley and no irrigation ditches for spawning. Fish numbers plummeted.

So now lots of money is being spent changing the river channels to incorporate a more meandering route, simulating the flooding affects of debris. Why didn’t they just remove the fish screens?

There has been (according to this) 0.7°C warming in the past century.
The irrigation has “hid” 0.1°C of the warming.
Therefore there should have been 0.8°C of warming.

Thus, we can see what is the solution.

Build many large desalination plants. Use the water to increase the amount of irrigated farmland eight times or more. That will “hide” all of the warming. We’ll go above eight times to cover the CO2 emissions from the coal-fired power plants needed. They’ll be placed along the shores of the neediest areas, Africa etc, where more food, especially locally grown food, will do a lot of good. There will also be a carbon sink effect, at least for awhile, some in the increased foliage compared to what was before, some in proper farming techniques leading to richer, more carbonaceous soil.

The needy will be fed, the warming will be offset, the planet will be saved. Oh, and that pesky “population bomb” -type problem from a projected 9 billion humans needing to fed in the near future will be taken care of.

I now await certain greenies to proclaim this is wrong because we certainly do not need any more of the agri-industrial complex that invariably destroys the environment and sickens the planet, the only cure is to return to the peaceful hunter-gatherer lifestyle of our ancient ancestors who lived in harmony with Mother Nature consuming only freely-available renewable resources… Whether they honestly word it that way or not.

“In a hundred years, the amount of irrigated farmland has grown four-fold, now covering an area four times the size of Texas.”… “Globally, irrigation’s effect on climate is small—one-tenth of one degree C”

If the figures are global and correct, we are talking about an increase from 0.13% to 0.54% of Earth’s surface.

Large areas of wetlands have been drained over the same time period, presumably offsetting the claimed cooling effect. Wetland loss is hard to estimate but over the C20th may be around 10 million square kilometres, or ~0.2% of Earth’s surface.

Whatever the effect then, it is small. Christy’s report was focussing on the effect of irrigation on local temperature stations designated as rural. The effect of those on the temperature records is likely to be a lot larger than the effect of irrigation on actual global temperature.

Wet soil will release water by evaporation and cool the soil due to the heat required for that as latent heat. When this water condenses this latert heat is given up so if this happens near the surface then local air temperatures will increase slightly. It also takes wet air longer to cool than dry air that is why temperatures plummet at night in dry desert regions and your beach side holiday has balmy warm nights.

As a Brit I was telling a visitor from Finland who was complaining at how cold it seemed even though she had felt warmer at temps down to -20 oC at home.I told her that Britain was damp, in the summer it was hot and damp, in the winter it was cold and damp and if it was neither hot or cold it was just damp.

John says:
September 8, 2010 at 5:11 pm…If you follow the link above back to the 2007 post on Christy’s study, you will see that Anthony did some analysis on Chico’s daily temps, and found — consistent with Christy — that nighttime temps were increasing for the last century. He also found — consistent with the new study — that daytime and daily average temps were decreasing with time, presumably as increased acreage became irrigated between 1900 and 2000…

There are too many other factors involved which make observing the small temperature differences seen as ‘evidence’ by both studies less than meaningful. Understanding micro-climates is very complex, as their interaction with the wider weather regime is dynamic with constant change to boundary conditions.

No firm conclusions can be made about climate impacts of these tiny changes until a better understanding of climate mechanisms is developed and more accurate observational data of much higher granularity is obtained.

More irrigation is a good place to start. Optimizing the total biosphere plant growth potential, is the goal we should be working toward as stewards of the planet, not the growth of wasteful government controls, or the manipulation of stocks and prices of commodities, or creating scare stories to lay the ground work for elitist control, resulting in the detriment of all life forms.

“LIFE forms are able to control the ionic and covalent bounds formed in the process of photosynthesis that binds energy into the making of compounds to build plant structure, that all other life forms digest to extract that energy of these covalent bonds to control all cellular functions.

Plants feed every thing else that lives!

In all cases where active building of compounds, from the basic constituents, are carried out in volume, there is a residual ionic charge carried out of the reaction area by electromagnetic conduction. In small single cell animals, their shapes are designed to most efficiently interface the internal EMF in a controlled way, to the external EMF that would modify or prevent the metabolism process, being conducted as needed by the animal to survive.

In large mammals and people there develops whole tuned structures that interface between organs like the liver that builds and disassembles glycogen for the storage of sugars.

The whole study of acupuncture, and the median lines of conduction woven through out the body is the result the study by those physically able to sense the EMF and coupling points on the skin surface, and at the same time understand the process of maintenance of the balance, phase, and polarity of total flux due to the whole continuum of life.

So that the median lines are the shared pathway of the EMF that is controllably shunted out of the chemical reaction to allow the flexible shifts in efficiency needed to prevent uncontrolled runaway feedback or disease processes that cause death.

Complex cells use semipermeable membranes, pores, vacuoles, and wall structure to do the bulk of the ion transfer related exchanges of the bulk materials. Homeostasis is an ever shifting balance between changing activity levels and internally regulated metabolic processes, and the outside chaos.

Rapid swings in temperature, humidity, Ph balance, gas content of the air, radiation levels that can, through the processes of ionization, inhibit or destroy the covalent bonds needed to maintain optimum health. Maintaining an enclosed dwelling with more environmental balance, so heat / cold related stress, oxidants external and internal and the virus and bacteria that are always trying for optimum cohabitation, are defended against.

All of these relationships are EMF in nature, and one should strive to be aware of their own inner balance and its relationship to the surrounding environment to maintain life energy levels close to optimum health.

Most plants and animals are aware of that and stay in tune with “the balance of nature” stress and other socially generated distractions prevent humans from moving with ease with in this sea of EMF we are constantly awash in. To ignore that this sea exists, and we are able to swim through it at will more easily by going with the shifts in the flows as they happen, only increases the level of disease one encounters.

To as a composite plant / animal biomass striving to maximum our total volume, it behooves us to be aware of how we can regulate our external environment, not just by avoidance of the problem areas, but by making changes in the background parameters that are outside of the optimum ranges for the whole biomass, not just in our dwellings.

If we do not understand how the weather is driven by ions, EMF, tidal effects, solar output, and the relationships between them, we will never learn the difference between what needs to be done, from what can be done to better optimize the global environment to maximize the health of the whole biomass.

Most farmers in all parts of the New World have seen major changes in local climates follow changes in land use and utilisation and understand the implications planting or removing forests, draining swamps and damming rivers, as examples, and have learnt much about the laws of unintended consequences as a result.
But the inhabitants of the old world of Europe and the UK live in landscapes that were modified aeons ago by the industries and farming practices of their forbears, but the changes to their environment are so far in the past that most are unaware of these processes and are highly resistant to any kind of visible change. I believe that this unawareness of historical change in land use is one of the sources of the Utopian silliness that comes from the Green lobby. I was amazed at the Government and Green responses to the serious flooding in the English Midlands a couple of years ago, when increassed rainfall due to alleged Man-made Global Warming was trumpeted as a cause for the flooding; anyone who pointed out that generations of covering flood plains with buildings, concrete and ashphalt was quite a dangerous thing to do was derided as a simpleton or an ignoramus.
I learnt in high school geography classes during the mid 1950s that large urban conurbations create their own warmer and wetter climate; has anything changed, apart from an increase in gullibility?

To tallbloke (1:02 am): Good point about draining of wetlands. A study which says that irrigation has caused 0.1% of warming to be blunted by increasing available moisture isn’t telling the complete story unless it also includes warming increases due to draining of wetlands. Roger Pielke Sr. gave a talk last spring where his group found that central Florida is about 2 degrees warmer than a century ago due to draining of the Everglades.

To Tenuc (2:12 am): I agree with your point that at the micro-climate level, there are too many things going on to draw conclusions based on only one parameter, in this case increasing irrigation.

But I wasn’t addressing whether the temperature trends identified by the two studies, and confirmed by Anthony in Chico, were caused by the one parameter, irrigation.

I was pointing out that there doesn’t actually seem to be a contradiction between the 2007 Christy et al work (which showed increased nighttime warming) and the new study (which shows increased daytime cooling). In fact, as in the 8:22 post above, Christy actually says that the daytime temps cooled, even as the nighttime temps warmed:

“While nighttime temperatures have risen, there has been no change in summer nighttime temperatures in the adjacent Sierra Nevada mountains. Summer daytime temperatures in the six county area have actually cooled slightly since 1910. Those discrepancies, says Christy, might best be explained by looking at the effects of widespread irrigation.”

That is from the 2007 presser you can access from the link above. So both studies agree on more daytime cooling the last century. No disagreement. And that was the only point I was addressing, that I didn’t see where the studies disagreed.

Scientists generally agree that in the last century, humans have warmed the planet about .7 degrees C (about 1.3 degrees F) by pumping vast amounts of carbon dioxide into the air.

Lat year, before Climategate, that would have been “Scientists overwhelmingly agree…” After all, way back then the science was settled, there was no debate, there was an overwhelming unprecedented peer-reviewed consensus that was historic in magnitude.

It’s far from a complete picture of the cyclonic processes because one has to take into account that there are changes in energy due to altitude and that the system is open; able to draw in e.g. less-humid air from around the storm, leading to further surface evaporation.

Processes are non-linear; often constrained by specific boundary conditions that are essentially unknowable. One can try to model them by making lots of assumptions, but other than a blurred picture, precise predictions are impossible. One can gain much more insight by pen on paper, procrastination, argument and watching the skies, seas and the land; than one can by diverting efforts into models that require very expensive computers and ending up naively obsessing about modelling artifacts.

This is all old hat. Irrigation tends to reduce temperature extremes, drainage to increase them, and more vegetation to reduce them. But unless the albedo changes quite a lot there’s not usually much effect on average temperatures.

Pamela Gray- exactly, well put…. Now we have “Hay Duke” Kitzhaber D-Retread
runnning for Oregon Governor, who wants to kill that flood control on the Snake, by blowing up the Snake River Dams.

The Grande Ronde and Wallowa Valleys will be covered with wind machines,
no people, or animals, imho, but that is what the appear to want…
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Yes that is exactly what they want they almost got it through the US Congress in one lump too (now they are implementing it peice by piece, they have not given up, just changed the name and toned down the message. (new improved version: http://www.twp.org/)

Water content in air naturally cools it, as water requires some 4000 times more energy to warm when compared same mass of air. So when water adds mass of air, as result temperature stays lower. On the otherhand water buffers also freezing, because freezing of water requires also more cold when compared to dry air.

Maybe the most important point however is the different nature of forest and swamp land when compared to crop land. As temperature is measured 2 metres above surfce of the earth, forest and swamp land are in nature cooler than cropland. This landscape change definitely must be taken into account when doing this type of research, otherwise it is nul reaserch.

Anecdotally – I am not sure if it is the irrigation or the fact you have living plants. But traveling along I8 in Imperial valley, there is a marked difference in termperature between the bare desert and the space between the canals.

The only way irrigation can only be a problem is when people first have absolutely gone overboard with drainage to boot. If you drainage too much you need to irrigate too much to saturate the ground enough and keep it saturated, and this is even disregarding the clogging factor. If you instead drainage smart you don’t need to irrigate that much in the first place, but you still have enough drainage to take care of most natural precipitation problems. There’s a whole friggin universe of problems that arise when your ground goes bone dry six feet down.

Well, this is typical of model-induced CAGW. GIGO, it depends upon the model, assumptions and what the researchers want to prove. For example:

Model Diagnosis of Nighttime Minimum Temperature Warming during Summer due to Irrigation in the California Central Valley
Hideki Kanamaru and Masao Kanamitsu
Scripps Institution of Oceanography, University of California, San Diego, La Jolla, California Abstract
This study examines the mechanisms of nighttime minimum temperature warming in the California Central Valley during summer due to irrigation. The Scripps Experimental Climate Prediction Center (ECPC) Regional Spectral Model (RSM) was used to simulate climate under two land surface characteristics: potential natural vegetation and modern land use that includes irrigation and urbanization. In irrigated cropland, soil moisture was prescribed in three different ways: 1) field capacity, 2) half of field capacity, and 3) no addition of water. In the most realistic case of half-field capacity, the July daily minimum temperature in the California Central Valley increased by 3.5°C, in agreement with station observation trends over the past century in the same area. It was found that ground heat flux efficiently keeps the surface warm during nighttime due to increased thermal conductivity of wet soil.

Here’s another paper (I forgot to cut and paste the Title, sorry), and another model output:

As discussed for a very similar model run in Kueppers
et al. (2007), the 1996 model results replicate quite
well many aspects of the Climate Research Unit (CRU)
0.5° × 0.5° gridded observations, which are derived from
surface station data (Mitchell and Jones, 2005). However,
the model has slightly greater, and more variable,
precipitation. The spatial patterns of the model and CRU
winter and summer near surface temperature and specific
humidity are very similar. However, the model has a cold
bias of about −3 °C and also a dry bias of about 15% of
the mean specific humidity. The biases for this domain
are similar in magnitude to those in three other models
(Kueppers et al., 2007). Preliminary investigations suggest
that these biases are related to the fact that the model
has persistent high thin clouds that reduces incoming
solar radiation at the surface forcing an artificially low
land skin temperature.

I grew up in a small farm town in the SJV and many of the farms that were there in my youth are now developments. UHI should also be taken into consideration when trying to figure out where the heat is coming from. It’s a hell hole in the summer that’s for sure.

I recall that the Columbia River froze every winter where it flows through Wenatchee, Chelan County, WA. Winter fog in Wenatchee was rare. Then two dams were built, one up river from Wenatchee (Rocky Reach) and the other downriver (Rock Island). Since then the rive no longer freezes and winter fog is common, enough to limit commercial air service to the area.

The dams that supply water irrigation to the Columbia River Basin influence seasonal weather far more the summer irrigation.

These two studies point to the heart of the global warming debate… real world data analysis versus cyber world theory manipulation. Do note Columbia’s computer analysis is over-generalized. The lead author says, “Irrigation can have a significant cooling effect on regular temperature.” “How much warming is being hidden by irrigation?”

John, I realize this is only an excerpt but irrigation warming is not mentioned.

Christy’s work looks at the world from the bottom up and uncovers two inconsistencies that the models do not see…boundary mountains responding differently from the valley and irrigation producing warming as well as cooling.

Columbia’s top down approach sees warming being hidden by irrigation cooling (well mixed carbon dioxide theory lingers in the background).

Chris here puts the emphasis where it belongs: on actual well-being. The AGW alarmists complain about what increases life or health; and praise what causes extinctions, suffering or hunger. Since so many people believe them, these econazis are a serious threat to your well-being and even your life. Not to mention “the environment.”

Let’s hope we see a followup article at WUWT from Dr Christy after he has had an opportunity to absorb this latest paper and has some time to write something. Nothing is as unsettled as real science. You have to go to Disneyland or Hollywood to find a clown who’ll tell you that all that is knowable is known about anything.

Christy mentions an increase in nighttime low temperatures by 5.5 F between 1910 and 2003. I would take this figure with a grain of salt if it relies on the same filtered data as NOAA, which as I understand it includes Sierra Nevada (high altitude, hence cool) temperatures in the early part of the century, which is removed from the data by the latter part. The NOAA valley temperature is derived from gridded data with interpolation from missing stations. The removal of NOAA data will introduce a fictional warming signal in central California. From that I don’t know what relative effects happen in the nighttime set, but it seems to me that it would be most extreme then, because as anyone familiar with high country will confirm, not only are temperatures cooler in general, but there is a larger daily variation at higher altitudes. Thus, nights are not only cooler because of the altitude but also because of a larger nighttime temperature swing.

Both of these studies appear to rely on cherrypicked data from regions with many peculiarities (a little less so in the latter case); it is a huge leap to isolate one particular causative factor out of many possible ones (such as urban development, drainage of swamps, deforestation, etc.) and attribute some climate factor change to that cause. Both studies, as far as I can tell from the articles, wave only vaguely at scientific principles that may explain such a connection but neither gives any actual theory demonstrating that, in principle, such an effect must occur.

I think a natural reply to both studies, even if one takes all data at face value, is “correlation is not causation”.

John-“That is from the 2007 presser you can access from the link above. So both studies agree on more daytime cooling the last century. No disagreement.”

Perhaps if you only look at the min and max separately and qualitatively, as you are doing, you might think these studies found the same thing. They did not. I can only explain this to you once more before I pull my hair out:

Christy found that the large min temp warming exceeded slight max temp cooling, so the mean trend was positive. But the study this post talks about says that the max cooling would exceeding the min temp warming, leading to net trends towards COOLING. Qualitatively these findings seem superficially similar, except in the trends in mean temps, but quantitatively they are very different.

R. Craigen-I am also only going to say this one more time, as I am tired of seeing people totally ignorant of what Christy did smearing himavailable that wasn’t previously! How dare you sir? by implying that he is using GISS or NOAA or GHCN data which is “flawed”. NO NO NO! Christy painstakingly assembled data himself. He does not MIX Sierra and Valley, he isolates them and uses data that none of the major groups use, PAINSTAKINGLY DIGITIZING THEM PERSONALLY (This is the thanks he gets for this hard, honest, careful book keeping?) where others simply ignored them. He did not “cherry pick” data, he went to great lengths to use all the data available and then to make data available that wasn’t already! READ THE DANG PAPER! UGH!

Water used per area of surface is being reduced by more efficient use such as drip/trickle feed, and monitoring fields with ability to control each sprinkler head independently. (Nothing like a shortage to motivate that – read The Doomsday Myth by Charles Maurice and Charles Smithson.)

But area may increase if the savings are still available for irrigation.